No chance have that many booked indirect. Some have of course but it won’t make a big dent in the allocation. 20k fans is pretty much 100 full flights. I’ve been using Skyscanner since before the semi and the same indirect flights are on sale now as were before. And they are flights which will be forecasted already to fill with non football fans.
Honestly, I believe people are getting way overhyped about demand for this. Plenty will do but plenty will not. I hardly know anyone who hasn’t fucked it off now because of price and hassle.
The most we’ve ever taken abroad is 8k to Porto and nearly everyone I know went to that.